Dr. Matthew Mccoy Editor Journal of Vertebral Subluxation Research

Wolf’s Law

Dr. Matthew McCoy

Editor – Journal of Vertebral Subluxation Research www.jvsr.com

It would be pretty hard to get out of chiropractic college without having heard of Wolf’s law though I’m uncertain as to the emphasis placed on it at our various schools. I’m especially uncertain about the emphasis in relation to subluxation theories and models.

Let’s remember that its Wolf’s Law, not Wolf’s Opinion and its one of the basic building blocks of the subluxation hypothesis.

Wolf’s Law states:

As bones are subjected to stress demands in weightbearing posture, they will model or alter their shape accordingly.

Wolf’s Law has a less well-known corollary for soft tissue called: Davis’ Law, that states:

Soft tissue will model according to imposed demands

While one could argue against these laws, just as one could argue that the sun won’t rise tomorrow, no one would take them seriously. These two Laws form the foundation of the rheology associated with subluxation and these rheological properties are essential elements in the epidemiology of vertebral subluxation.

Rheology is the study of the change in form and the flow of matter including elasticity, viscosity and plasticity and epidemiology is the study of the elements contributing to the occurrence of disease.

No matter which of the various models of vertebral subluxation one chooses to discuss there are two components that are common to all models. These components are Kinesiopathology and Neuropathology. The following is a step-by-step overview of the changes that take place secondary to abnormal movement and alignment of vertebrae (kinesiopathology). It’s not the most exciting reading but these concepts are essential if one is to understand the nature and character of vertebral subluxation.

1. Physiologic loads of tension cause increased aggregation of collagen. Compression has the opposite effect

2. Collagen fibers are laid down in response to stress lines of mechanical loads

3. The metabolic activity of connective tissue cells is (increased) also affected by mechanical forces/stress

4. Collagen under compressive and tension creates different distributions of electrical charge

5. There is increased attachment of proteoglycans, attachment of new collagen fibers, loss of water and unattached proteoglycans.

6. Fibers are shortened by remodeling

7. An increase in stress causes an increase in collagen production and organization

8. A decrease in stress causes a decrease and disorganization of collagen fibers

9. Collagen is permanently lengthened only by denaturing and weakening the fibers, which occurs when the tissue is subjected to excessive strain.

10. The development of fibrosis is preceded by an accumulation of inflammatory cells within a tissue.

11. Tissues that are compressed tend to fold upon one another. This folding may be the critical factor that promotes interfibrillary adhesions

12. Any alteration in the degree or type of physiologic loading is followed by changes in cellular metabolism, matrix morphology, and functional capacity.

13. Cells, Glycosaminoglycans, and collagen type and architecture are all affected by the direction and magnitude of physical stress applied to a tissue.

14. The degeneration of the articular cartilage begins with mild fraying of the tangential collagen fibers (fibrillation) followed by cavitation (blistering) between the tangential collagen bundles.

15. Blistering is succeeded by vertical splits (clefting) that penetrate the superficial layer and then the deep layers.

16. The clefted cartilage is gradually worn away leading to a complete denuding of affected regions of the articular surface.

17. This process leads to a marked alteration in the porosity of cartilage and alteration of fluid flow through it.

18. Immunocompetent cells and immunoglobulins obtain access to normally protected deeper cartilage layers

19. According to Wolff’s law, bones remodel to resist an applied stress

20. As a bone is stressed, regions subjected to compression become more electronegative while areas subjected to tension become more electropositive.

21. The osteophytes respond by manufacturing additional bone on the electronegative surface and removing it on the electropositve surface.

22. These mechanically generated electrical signals are monitored and averaged to influence osteocyte metabolism.

23. A bioelectric signal is generated via a piezoelectric effect and transduced by the osteocytes, which remodel the bone to resist the stress.

Genu Valgum, Pediatrics

Last Updated: February 11, 2006 / Rate this Article
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Synonyms and related keywords: physiologic genu valgum, pathologic genu valgum, adolescent idiopathic genu valgum, knock-knee deformity, osteotomy, hemiphyseal stapling, vitamin D resistant rickets, vitamin D-resistant rickets, guided growth, 8-plate
AUTHOR INFORMATION / Section 1 of 11
Author Information Introduction Indications Relevant Anatomy And Contraindications Workup Treatment Complications Outcome And Prognosis Future And Controversies Pictures Bibliography
Author: Peter M Stevens, MD, Professor, Director of Pediatric Orthopedic Fellowship Program, Department of Orthopedics, University of Utah School of Medicine
Coauthor(s): Michael C Holmstrom, MD, Consulting Surgeon, Department of Orthopedics, The Orthopedic Specialty Hospital (TOSH)
Peter M Stevens, MD, is a member of the following medical societies: AO Foundation, Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American Orthopaedic Association, and Pediatric Orthopaedic Society of North America
Editor(s): Mininder S Kocher, MD, MPH, Assistant Professor of Orthopedic Surgery, Harvard Medical School, Director, Orthopedic Institute for Clinical Effectiveness, Children's Hospital of Boston; Consulting Surgeon, Department of Orthopedic Surgery, New England Baptist Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; George H Thompson, MD, Professor of Orthopedic Surgery and Pediatrics, Case Western Reserve University; Director, Department of Pediatric Orthopedic Surgery, Rainbow Babies and Children's Hospital; Dinesh Patel, MD, Assistant Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; and Dennis P Grogan, MD, Clinical Professor, Department of Orthopedic Surgery, University of South Florida College of Medicine; Chief of Staff, Department of Orthopedic Surgery, Shriners Hospital for Children of Tampa
Disclosure
INTRODUCTION / Section 2 of 11
Author Information Introduction Indications Relevant Anatomy And Contraindications Workup Treatment Complications Outcome And Prognosis Future And Controversies Pictures Bibliography
Genu valgum is the Latin-derived term used to describe knock-knee deformity. While many otherwise healthy children have knock-knee deformity as a passing trait, some individuals retain or develop this deformity due to hereditary or genetic disorders or metabolic bone disease. The typical gait pattern is circumduction, requiring that the individual swing each leg outward while walking in order to take a step without striking the planted limb with the moving limb. Not only are the mechanics of gait compromised but also, with significant angular deformity, anterior and medial knee pain are common. These symptoms reflect the pathologic strain on the knee and its patellofemoral extensor mechanism.
For persistent genu valgum, treatment recommendations have included a wide array of options, ranging from lifestyle restriction and nonsteroidal anti-inflammatory drugs to bracing, exercise programs, and physical therapy. In recalcitrant cases, surgery may be advised. No consensus exists regarding the optimal treatment. Some surgeons focus (perhaps inappropriately) on the patella itself, favoring arthroscopic or open realignment techniques. However, if valgus malalignment of the extremity is significant, corrective osteotomy or, in the skeletally immature patient, hemiepiphysiodesis may be indicated.
Osteotomy indications and techniques have been well described in standard textbooks and orthopedic journals and are not the focus of this article. Hemiepiphysiodesis can be accomplished using the classic Phemister bone block technique, the percutaneous method, hemiphyseal stapling, or, more recently, application of a single 2-hole plate and screws around the physis. The senior author, having experience in each of these techniques, has developed the later technique in order to solve 2 of the problems sometimes encountered with staples, namely hardware fatigue and migration. The rationale and versatility of this technique for managing genu valgum are the emphasis of this article.
History of the Procedure: The focus of this article is the indications, techniques, complications, and outcome of guided growth using the reversible plate technique for the correction of pathologic genu valgum. Since the introduction of staples by Walter Blount in 1949, this procedure has waxed and waned in popularity and remains the subject of criticism and controversy. Indeed, some recent review articles and book chapters dismiss stapling as a historical procedure, citing unpredictability and the fear of permanent physeal arrest as results of stapling. While stapling can work well, occasional breakage or migration of staples can necessitate revision of hardware or premature abandonment of this method of treatment.
Some surgeons have reverted to osteotomy of the femur and/or tibia-fibula as the definitive means of addressing genu valgum. However, this is a very invasive method fraught with potential complications, including malunion, delayed healing, infection, neurovascular compromise, and compartment syndrome. Further complicating the picture, these deformities are often bilateral, requiring a staged correction. The aggregate hospitalization, recovery time, costs, and risks make osteotomy a last resort for angular corrections (unless the physis has already closed).
Percutaneous drilling or curettage of a portion of the physis yields only a small scar and no implant is required. However, this is a permanent, irreversible technique. Therefore, its use is necessarily restricted to adolescent patients and is predicated upon precise timing of intervention, requiring close follow-up to avoid undercorrection or (worse yet) overcorrection.
Some authorities advocate using percutaneous epiphyseal transcutaneous screws as a means of achieving angular correction. While this is performed through a small incision, the physis is violated and the potential exists for the formation of an unwanted physeal bar, with its sequelae. To date, its no potential for reversing the procedure has been document; therefore, the only reported cases have been in adolescents.
By comparison, guided growth, using a nonlocking 2-hole plate and screws, is a reversible and minimally invasive outpatient procedure, allowing multiple and bilateral simultaneous deformity correction. A single implant (the authors prefer the Orthofix [McKinney, Tex] 8-plate) per physis; this serves as a tension band, allowing gradual correction with growth. Because the focal hinge of correction is at or near the level of deformity, compensatory and unnecessary translational deformities are avoided.
The previous empirical constraints related to the indications, including appropriate age group and the etiology of deformity, have been successfully challenged using this technique, with consistently good results. In a personal series of more than 100 patients, ranging in age from 19 months to 17 years, and some with pan-genu deformities, the senior author has not had a permanent physeal closure.
Problem: Normal alignment means that the lower extremity lengths are equal and the mechanical axis (center of gravity) bisects the knee when the patient is standing erect with the patellae facing forward. This position places relatively balanced forces on the medial and lateral compartments of the knee and on the collateral ligaments, while the patella remains stable and centered in the femoral sulcus.
In children younger than 6 years, physiologic genu valgum is common but is self-limiting and innocuous. In children (of any age) with pathologic valgus, when the mechanical axis deviates into or beyond the lateral compartment of the knee, regardless of the etiology, a number of clinical problems may ensue. Medial ligamentous strain may be associated with recurrent knee pain. The patellofemoral joint may become shallow, incongruous, or unstable, causing activity-related anterior knee pain. In extreme cases, frank patellar dislocation with or without osteochondral fractures may ensue.
Because patellar dislocation reflects an insidious and progressive growth disturbance, nonoperative management relying on physical therapy and bracing is of little value. During the adult years, premature and eccentric stress on the knee may result in hypoplasia of the lateral condyle, meniscal tears, articular cartilage attrition, and arthrosis of the anterior and lateral compartments.
Frequency: Adolescent idiopathic genu valgum may be familial, or it may occur sporadically. The true incidence is unknown. Certainly it is one of the most common causes of anterior knee pain in teenagers and is a frequent reason for orthopedic consultation. Likewise, the incidence of the predisposing syndromes is difficult to ascertain. Predisposing syndromes, such as hereditary multiple exostoses, Down syndrome, and skeletal dysplasias, are more apt to manifest in patients aged 3-10 years, and valgus may become severe if untreated. Regardless of the etiology, surgical correction of significant and symptomatic malalignment is warranted, regardless of the age of the patient.